Show CHARCOAL precipitation J FROM CYANIDE SOLUTIONS research work is being continued by the department of the interior at the rare and precious metals experiment station of the bureau of mines reno nevada to determine whether the use of charcoal for precipitating gold and silver from cyanide solutions is feasible if charcoal could be used it would have many advantages on account of its cheapness it has been found that charcoal would precipitate gold and silver from a cyanide pulp ore an and d cyanide solution and that this loaded charcoal could be readily at floated away from the p pulp counter current charcoal pre capitation on tonopah extension mill solution proved satisfactory is acting very quickly with complete precipitation on fairly coarse 50 mesh charcoal many kinds of charcoals were tested and many different treatments of charcoal tried for their precipitating efficiencies the general conclusion arrived at was that no charcoal has any outstanding advantage over any other most treatments of charcoal that give advantageous results can be traced to a heat treatment men t whereby oxidation of the inert carbon is effected either by air or steam very few fouling agents in cyanide solutions affect the precipitation of gold or silver bonchar on charcoal one of the principal problems is to recover the precipitated metals A number of solvents were found for the gold or silver precipitated on charcoal these generally act much more vigorously if hot A hot cyanide solution is a very effective solvent for both gold and silver hot water dissolves a considerable amount of gold and silver electrolytic separation of the precipitated gold or silver on charcoal from cyanide gave only indifferent results and does not appear promising promising results were obtained in the use of sodium sulphide in connection with charcoal as a silver precipitant cyanide is regenerated in this case and excess of sodium sulphide is taken care of by absorption on the charcoal if the excess is not too large this sulphide charcoal precipitation is is detrimental however in gold precipitation the theory that some chemical treatment of a loaded charcoal would so change the absorbed gold and silver a as to reactivate activate re the charcoal for a new load was given some attention such a chemical may be called a fixer it was found that nitric acid has some power as a fixer but that hydrochloric acid has none more experimental work is is needed to determine whether reactivation would be a feasible step in a charcoal process much progress has been een made by the bureau of mines in working out the chemistry of the process and fundamental data have been obtained on the mechanism of the precipitation of gold and silver on charcoal |